[RJR_38]

I got an apple tree at Easter which I planted out with mychorizzal fungus and plenty of rotted manure mixed in with the soil. I popped down quickly today to drop off some soil and noticed that around a third the leaves look a much paler green than the others and some of the darker green ones have some brown looking spots on them. There are only about 10 like this but I want to make sure it isn't anything serious. If there are any solutions I would much rather have organic as I don't use chemicals

[BabbyAnn]

I wouldn't worry too much about leaf colour at this time of year - leaves coming on are being subjected to a mix of bright and dull days so probably not a lot of photosynthesis going on at a time when there is rapid growth.

As for brown spots - as well as possible sun scorch, you can also get insects and caterpillars that burrow into leaves.  Another possibility (although I'd say a bit early to be showing signs) is apple canker - this will show as blemishes on the fruit though.

With regards "organic" methods, you could try adding potash to the soil, and to control insects (especially things like codling moths), have a look at glue/grease bands and pheromone traps (cost about £7 on e-bay and contains 2 treatments for the year) 

[RJR_38]

I had a good look today and couldn't see any caterpillars but I will keep a look out. It's my first fruit tree so I don't want to kill it straight away!

[Goosegirl]

I thought it might be sun scorch due to droplets of rain left on the leaf where they act as a kind of heat mirror and literally burn the leaf. The leaf in your picture has a bigger mark towards the end of the leaf where smaller droplets may have run down to form a bigger one.

[RJR_38]

That would make sense to be fair as the leaves are predominantly on one side - so I guess that's where the angle of the sun was at the time. I will stop worrying for now then!

[ConfusedGardener]

I'm fairly confident that plain water on leaves causing burns is a myth. If it was true then there would be many burnt leaves everywhere when bright sun follows rain, and that is never the case in my experience. Also, I don't think the physics makes sense - lenses tend to have their focal-points (which is where any burn would occur) a significant distance behind the lens, which would be on the other side of the leaf, so the light would not be able to come to a focus on the leaf surface.

I think an exception might possibly be tiny droplets that form near perfect spheres whilst sitting on the leaf surface or leaf hairs, but even they would only cause "pin-prick" sized burns. I suspect even this would be rare since such tiny droplets would soon evaporate (and/or be absorbed by the leaf) under most circumstances.

The only way water on a leaf might cause a burn is if there was something else in the water, which would become more concentrated as the water evaporated, up to the point of potentially burning the leaf. Foliar feeding with chemical fertilisers for example.